Multiple vehicle subsystems, such as the vehicle brakes, may utilize vacuum as an actuation force. The vacuum is typically supplied by the engine through a connection to the intake manifold, which is at sub-barometric pressure when the throttle is partially closed and regulating the airflow into the engine. However, the engine intake manifold vacuum may not be sufficient for all of the subsystems at all operating conditions. For example, during a catalyst heating mode immediately after engine starting, a high level of spark retard may be used to generate exhaust heat directed to the catalyst, resulting in insufficient vacuum from the intake manifold.
The inventors have recognized the issues with the above approach and offer a system to at least partly address them. In one embodiment, a system comprises a throttle positioned in an intake of an engine, and a peripheral venturi proximate the throttle, the venturi having an inlet positioned to interface with an edge of the throttle when the throttle is in a partially open position.
In this way, vacuum may be generated by the peripheral venturi when the throttle is partially opened, e.g., at an angle that may not produce a sufficient pressure drop across the throttle to generate adequate vacuum in the intake manifold. The size of the venturi inlet and positioning relative to the throttle may be based on the throttle angle typically used during conditions where intake manifold vacuum is not sufficient, such as during the catalyst heating mode described above. By routing a portion of the intake air through the venturi, vacuum may be generated during conditions of low intake manifold vacuum.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.